柱前衍生-高效液相色谱法测定婴幼儿谷类辅食中的甲醛

目的建立柱前衍生-高效液相色谱法测定婴幼儿谷类辅食中甲醛含量的分析方法。方法样品中的甲醛经柠檬酸钠缓冲溶液和含有2,4-二硝基苯肼的乙腈混合体系衍生提取,生成的甲醛-2,4-二硝基苯腙经色谱柱Agilent Poroshell 120 EC-C18(4.6 mm×150 mm, 2.7μm)以乙腈-水(70:30, V:V)等度洗脱分离,柱温30℃,流速为0.5 mL/min,检测波长为355 nm,外标法定量分析。结果甲醛在0.025～2.00 mg/L质量浓度范围内线性关系良好且相关系数(r2)大于0.995,方法检出限和定量限分别为0.03 mg/kg和0.10 mg/kg,在3个加标水平(1.00、5.00和10.0 mg/kg)的平均加标回收率为86.8%～89.0%,相对标准偏差为0.7%～2.1%。结论该方法操作简便,灵敏度高,重现性好,适用于婴幼儿谷类辅食中甲醛含量的测定。     

Mergers and acquisitions in radio and television broadcasting: Consistent goals and adaptive regulation

Radio and television broadcasting regulatory policy is fraught with challenges due to rapidly changing technologies and therefore potentially fluid markets. The evolution of regulatory policy in the United States has been relatively adaptable, while policy goals remain constant by comparison. This paper seeks to identify the most important issues regulators face when considering the broadcasting industry generally, and to provide a guide to an adaptive regulatory environment in which mergers and acquisitions in the radio and television industries can exist, based on the U.S. experience.     

Reduction of Escherichia coli O157, Listeria monocytogenes and Salmonella enterica sv. Typhimurium populations on fresh-cut bell pepper using gaseous ozone

Bacterial contamination is the main cause of food poisoning which can lead to diarrhoea, abdominal cramp, vomiting as well as death. Bacterial contamination can potentially be controlled by application of gaseous ozone due to its antibacterial activity. Therefore, the objective of this study was to investigate the efficacy of gaseous ozone for reducing food-borne pathogens such as Escherichia coli O157, Listeria monocytogenes and Salmonella enterica sv. Typhimurium on fresh-cut bell pepper. Efficacy of gaseous ozone to reduce bacterial populations was investigated in vitro and in vivo. Results showed that optimum effect of ozone on reducing bacterial populations was achieved with short term exposures of less than 6 h. Ozone reduced the bacterial population by disrupting bacterial cell structure, which lead to cellular death. Results also showed that bacterial cells have different resistance to ozone where ozone was more effective against L. monocytogenes, followed by E. coli O157 and Salmonella Typhimurium. Optimal reduction of the bacterial population on fresh-cut bell pepper was achieved with exposure to 9 ppm ozone for 6 h. This treatment reduced 2.89, 2.56 and 3.06 log of E. coli O157, Salmonella Typhimurium and L. monocytogenes populations, respectively. In conclusion, exposure to 9 ppm ozone for 6 h helps in reducing food-borne pathogen on fresh-cut bell pepper and has high potential to be an alternative sanitization treatment to reduce pathogen population on fruit.